With applications ranging from diagnostic procedures to radiation therapy, the importance of high-performance medical imaging is immeasurable. As such, new advanced medical imaging technologies continue to be developed. Some such imaging systems utilize amorphous silicon flat panel x-ray detectors.
Generally, in amorphous silicon flat panel x-ray detectors, an amorphous silicon array is disposed on a glass substrate, and a scintillator is disposed over, and is optically coupled to, the amorphous silicon array. An x-ray source emits a beam of x-rays towards the scintillator, which absorbs the x-ray photons and converts them to visible light. The amorphous silicon array then detects the visible light and converts it into electrical charge. The electrical charge at each pixel on the amorphous silicon array is read out digitally by low-noise electronics, and is then sent to an image processor. Thereafter, the image is displayed on a display, and may also be stored in memory for later retrieval.
Scintillators generally comprise materials that are matched to the type of radiation being used. Cesium iodide is one typical material that medical radiation imaging scintillators may comprise. Cesium iodide is an inorganic compound that is grown on the device, in the form of needles, by chemical vapor deposition. Cesium iodide is a hygroscopic, air sensitive, oxidizing material, and therefore, requires a protective barrier coating thereon to prevent the cesium iodide from deteriorating upon contact with ambient conditions. Typically, this protective barrier coating comprises a transparent non-reflective material, such as, for example, Parylene-N, Parylene-C, or Parylene-D. Additionally, a reflective layer is also generally required on top of the coated cesium iodide needles, to improve the light reflection and/or light conducting properties of the cesium iodide needles, and to reflect the light back into the needles and prevent it from scattering out therefrom, thereby improving the device performance. Typically, this reflective layer comprises a sheet of material, such as Opticlad; a white colored, highly reflective plastic material that is placed on top of the coated cesium iodide layer.
Since existing scintillators require both a protective barrier coating and a reflective layer of some sort, it would be desirable to have protective barrier coatings that are also reflective coatings, so that a single coating or layer could be used as both a protector and a reflector. It would also be desirable to co-deposit a protective barrier coating and a reflective coating at the same time, so as to minimize the number of processing steps that are required to manufacture the scintillators, thereby resulting in a single coating or layer that acts as both a protector and a reflector.